Torque wrench with overload release means



Jun@ 12, F'. L KE'EN TORQUE WRENCH WITH ovERLoAD RELEASE MEANS FiledJan. 27, 1948 Patented June 12, 1951 TORQUE WRENCH WTH OVERLGAD YRELEASE MEANS Frank Leslie Keen, Llandaff, near Cardi, Wales ApplicationIlanuary 27, 1948, Serial No. 4,562 In Great Britain March 20, 1947 3Claims.

This invention relates to improvements in torque wrenches such as areused where it is important in tightening a nut on a bolt or stud that adefinite amount of tension is exerted, in order that the part or partsto be secured by the nut and bolt or stud are rmly and permanentlysecured together. It will be apparent that in tightening a nut with atorque wrench, a certain optimum torque may be applied, which whilstgiving sufficient tension must not approach the value at which the boltor stud may break under the tension applied. In cases where it is vitalthat an exact safe tension be applied, such as in automobile or aeroengines, some means must be provided, whereby the amount of tension onthe bolt or stud is controlled.

The object of the present invention is to provide a simple but reliablewrench which may be used readily as in the manner of an ordinary wrench,but does not permit the desired tension to be exceeded by the personoperating the wrench. It is a further object of the invention to providea means, whereby a considerable. range of tension may be effected by asimple adjustment to the wrench.

According to the invention the torque wrench comprises a lever handlefurnished with a head at one end constituting a housing for a camrotatable therein, said cam having means for receiving a socketed heador jaw and resilient means bearing on said cam to restrict the rotationthereof.

Preferably, the lever handle is of tubular form to receive a springadapted to bear on a roller engaging in a recess in the rotatable cam.The handle is tted with a head which embraces the cam and provides abearing surface therefor, the cam being enclosed by side plates throughone of which a squared lug projects for engagement with the known typeof castellated nut, socketed head or jaw. The spring loading applied tothe roller holds the cam against rotation until the leverage issuiciently great to cause the cam to Adetachable jaw which may beattached by insertion on to a lug or other convenient means at the headof the wrench. 'I'he torque wrench comprises a tubular lever handle I3fitted with a head i4 which serves as a housing for a pair of ball racesl5, l5 which support a cam I6.

The cam is formed with a pair of trunnions il, l1 which engage the innerraces of the ball bearings one of the trunnions being extended as at I8to provide a squared end for engagement with a socketed head or jaw.'I'he lever handle I3 houses a spring I9, one end of vwhich is engagedby an adjustable plug 2Q and the other end of which bears` on a tappetor rocker member 2|. The member 2l is suspended by means of a pair oflinks 22, 22 to which it is pivoted at 23, 23 the other ends of thelinks being pivoted at 24, 2li within an enlargement 25 formed in thehead of the wrench, the member 2| is thus capable of swinging to and froagainst the action of the spring I9 when moved by the cam i6. 'I'hemember 2| rotatably supports a roller 26 which er1- gages a concave part2T formed in the periphery of the cam I9.

An advantage arising from the invention is that friction due to movingparts of the device is considerably reduced. Friction may be reducedfurther by mounting the links 22 and roller 2t on needle type roller andbearings.

Principle of operation of the torque wrench is as follows:

The torque is built up through the compression of a spring acting on apivoted rocker member which carries a roller. A plunger holds the springunder compression and through the medium of the roller running over thecontour of a special cam sets up a torque reaction which reaches itsmaximum just before the roller reaches the concentric track of the cam.

When the roller has reached the concentric track of the cam, the torquereaction breaks down, and as there is no further contour for the rollerto run up, the roller runs round the cam, until it again reaches thecavity in the cam, into which it is now pushed by the spring.

The wrench is now ready for another torque test, and depending on thenumber of cavities or cam contours situated round the operating cam sowill there be an equivalent number of torque impulses per revolution oftorque wrench handle round the axis of the cam.

Thus, .if a suitable attachment is fitted to the cam centre, such as asocketed head, or jaw, the torque reaction set up by rotating the wrenchhandle around the axis of the cam, will be transmitted to the nut orbolt, through the medium of the socketed head or jaw and will thusaccurately torque load said nut or bolt to the pre-set loading of thespring.

What I claim and desire to secure by Letters Patent is:

l. A torque wrench comprising a hollow handle, a hollow .head'at one endof the .handle-a rotatable cammdunted in 'said head, said cam having arecess in its peripheral surface and axial means for engaging a memberto be rotated by said wrench, a rocker member pivotally mounted in saidhead on a pivot which is disposed in offset relation to the axis of thehandle, a roller 'carried by said rocker member, and spring''meansyWithin the handle biasing said rocker member to normally hold theroller Within the'recessinthe'eam so that the cam will move with thehandle as a unit when less than a predetermined torque lis applied tothe cam, andwhen a torque in excess .of the predetermined-torqueisapplied -to the/cam =therollervvill ride out of the-eam-reeessandfover the periphery of the cam and the handle will vmove relativelyto the cam. v

2. A torque Wrench according to claim l wherein the force of the springmeans is transmitted through the rocker member to the roller in adirection substantially parallel t0 the axis of the handle.

3. A-torque'wrench according'to claim 1 wherein .the pivotal mountingfor the rocker member is provided by a pair of parallel links.

FRANK LESLIE KEEN.

REFERENCES CITED vThe following references are of record in the le ofthis patent:

vrUNITED STATES PATENTS Morris Dec. 19, 1944

